In general, with regard to laminated glass used as a windshield of a motor vehicle, etc., scattering of glass pieces when broken is prevented by compression bonding, between exterior glass on the outside of the vehicle and interior glass on the inside of the vehicle, an intermediate layer formed from a resin such as polyvinyl butyral or vinyl chloride.
Furthermore, a so-called head up display is known in which a variety of information is visibly displayed on a windshield so as to be provided to a driver. FIG. 5 shows one example of such a head up display; an image display section 02 formed from a half mirror (combiner) is provided on the surface of a windshield 01 on the inside of a vehicle, and an image 02a projected by an image projector 03 provided on a dashboard is reflected by the image display section 02 and imaged a few meters in front of the windshield 01, thereby enabling the image 02a to be viewed by the driver.
However, since the combiner is semi-transparent, when it is provided over a wide area of the windshield, the field of vision of the driver through the windshield is obstructed, and there is the problem that it is not possible to ensure a sufficiently large area for the combiner.
An arrangement in which a transparent light-emitting layer supporting phosphor particles is disposed on the interior of a windshield, and the layer is irradiated with ultraviolet light so as to excite the phosphor particles to make them emit light, thereby displaying an image on the light-emitting layer has been proposed. However, part of the light emitted forward from the image on the light-emitting layer is reflected from the surface of the windshield on the outside of the vehicle and reaches the eye of the driver. Because of this, a real image formed from light emitted directly from the image on the light-emitting layer and a reflected image of the image reflected from the surface of the windshield on the outside of the vehicle are visible to the driver one on top of another as shown in FIG. 3. In order to prevent this, the windshield 01 may be disposed perpendicular to the direction of the line of sight of the driver, but this is difficult for reasons of aerodynamics or design.
In the arrangement disclosed in Patent Publication 1 below, the thickness of a windshield having its upper side inclined rearward is changed so that the further toward the lower side the thinner it is, thus minimizing the displacement between a real image and a reflected image of an image on a light-emitting layer and thereby improving the visibility.    Patent Publication 1: Japanese Patent Application Laid-open No. 2-279437